lisa.utils.group_by_value

lisa.utils.group_by_value(mapping, key_sort=<function <lambda>>)

Group a mapping by its values

Parameters:

• mapping (collections.abc.Mapping or collections.abc.Sequence) – Mapping to reverse. If a sequence is passed, it is assumed to contain key/value subsequences.

• key_sort (collections.abc.Callable) – The key parameter to a sorted() call on the mapping keys

Return type:

collections.OrderedDict

The idea behind this method is to “reverse” a mapping, IOW to create a new mapping that has the passed mapping’s values as keys. Since different keys can point to the same value, the new values will be lists of old keys.

Example:

>>> group_by_value({0: 42, 1: 43, 2: 42})
OrderedDict([(42, [0, 2]), (43, [1])])